我正在尝试发送一个DatagramPacket,然后必须等待来自服务器的Acknowlegment,以便我知道是否必须重新发送相同的数据包或发送下一个数据包.
我在客户端使用相同的套接字,发送数据包并接收确认(ack),在服务器端使用相同的,另一个套接字用于接收数据包,然后将确认发送给客户..
第一个问题是客户端正在发送数据包,服务器正在接收它,然后将确认发送给客户端,但客户端在接收确认数据包时阻塞.
我正在制作一些System.out.println以确定问题所在,但我无法找到解决此问题的方法.
第二个问题是服务器仍然总是接收数据,并且不要等待客户端发送内容,我检查了因为我得到了那些行(例如“得到长度为xxx的数据包”“ack与ackNr yyy一起发送”… “虽然客户端在发送第一个数据包后仍在阻塞,但始终打印在服务器端,因为它正在等待未收到的确认！
这是CLIENT的代码：
package blatt7;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketTimeoutException;
import java.net.UnknownHostException;
import java.nio.ByteBuffer;
import java.util.zip.CRC32;
public class FileSender {
String zielRechner;
String filePath;
InetAddress host;
File file;
FileInputStream fis;
int readLength;
int sequenceNr = 0;
int receivedSeqNr = 1;
static int port = 7777;
int packetNr = 0;
byte[] packet = new byte[1216];
byte[] data = new byte[1200];
byte[] header = new byte[16];
byte[] readLengthByte = new byte[4];
byte[] sequenceNrByte = new byte[4];
byte[] checksumByte = new byte[8];
byte[] ackBuffer = new byte[4];
CRC32 checksumCalculator = new CRC32();
DatagramPacket dp;
DatagramPacket ackPacket;
DatagramSocket sendSocket = null;
//DatagramSocket ackSocket = null;
static boolean ackReceived = true;
public FileSender(String zielRechner,String filePath) throws UnknownHostException,FileNotFoundException {
this.zielRechner = zielRechner;
this.filePath = filePath;
this.host = InetAddress.getByName(zielRechner);
this.file = new File(filePath);
fis = new FileInputStream(file);
}
public void sendFile() throws IOException {
while((readLength = fis.read(data)) != -1) {
if (sequenceNr == 1)
sequenceNr = 0;
else
sequenceNr = 1;
readLengthByte = intToBytes(readLength);
sequenceNrByte = intToBytes(sequenceNr);
for(int i=0; i<4; i++) {
header[8+i] = readLengthByte[i];
}
for(int i=0; i<4; i++) {
header[12+i] =sequenceNrByte[i];
}
int j=0;
for (int i=0; i
这是SERVER的代码：
package blatt7;
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;
import java.util.zip.CRC32;
public class FileReceiver {
byte[] incomingBuffer;
DatagramPacket incomingPacket;
DatagramSocket receiveSocket;
DatagramPacket ackPacket;
int packetCounter = 0;
int dataLength;
int receivedSeqNr;
long calculatedChecksum;
long receivedChecksum;
CRC32 checksumCalculator = new CRC32();
byte[] dataLengthByte = new byte[4];
byte[] receivedSeqNrByte = new byte[4];
byte[] receivedChecksumByte = new byte[8];
byte[] ackArray;
public FileReceiver() throws SocketException {
incomingBuffer = new byte[1500];
incomingPacket = new DatagramPacket(incomingBuffer,incomingBuffer.length);
}
public void receive() throws IOException {
receiveSocket = new DatagramSocket(FileSender.port);
receiveSocket.setSoTimeout(10000);
System.out.println("Server socket created. Waiting for incoming data...");
while(true && FileSender.ackReceived)
{
receiveSocket.receive(incomingPacket);
packetCounter++;
for (int i=0; i <4; i++) {
dataLengthByte[i] = incomingBuffer[8+i];
}
dataLength = FileSender.bytesToInt(dataLengthByte,0);
checksumCalculator.reset();
checksumCalculator.update(incomingBuffer,dataLength+8);
calculatedChecksum = checksumCalculator.getValue();
for (int i=0; i <4; i++) {
receivedSeqNrByte[i] = incomingBuffer[12+i];
}
receivedSeqNr = FileSender.bytesToInt(receivedSeqNrByte,0);
for (int i=0; i <8; i++) {
receivedChecksumByte[i] = incomingBuffer[i];
}
long receivedChecksum = FileSender.bytesToLong(receivedChecksumByte,0);
System.out.println("Got packet with checksum: " + receivedChecksum);
System.out.println("Server-calculated checksum: " + calculatedChecksum);
System.out.println("Got packet with seqNr: " + receivedSeqNr + " and length: " + dataLength);
if (calculatedChecksum != receivedChecksum) {
sendACK(receivedSeqNr);
System.out.println("Packet have erros(s)! It must be sent another time!");
}
else if(calculatedChecksum == receivedChecksum && receivedSeqNr == 1) {
sendACK(0);
System.out.println("SeqNr '0' sent");
}
else if (calculatedChecksum == receivedChecksum && receivedSeqNr == 0) {
sendACK(1);
System.out.println("SeqNr '1' sent");
}
}
}
public void sendACK(int seqNum) throws IOException {
byte[] ackArray = FileSender.intToBytes(seqNum);
ackPacket = new DatagramPacket(ackArray,ackArray.length,InetAddress.getByName("localhost"),FileSender.port);
receiveSocket.send(ackPacket);
}
public static void main(String[] args) throws IOException,ClassNotFoundException {
FileReceiver receiver = new FileReceiver();
receiver.receive();
}
}
您可以尝试执行它以查看问题所在……
所以,如果你有任何想法我怎么能解决这个问题,请告诉我！
非常感谢你！
谁能告诉我在哪里可以找到收到的文件？或者我应该如何更改我的代码,以便我选择保存它的位置？
对的,这是可能的.您的问题是您在发送ACK数据报时遇到目标地址：端口错误.您应该从接收到的DatagramPacket获取目标地址：端口,或者更简单地仍然只是将具有不同数据的数据报重用为ACK数据报.
